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1. Field of the Invention
This invention relates generally to techniques for cooling dissipative electrical and electronic components, and, more particularly, to a technique for cooling such components on circuit boards through the direction of exhaust air.
2. Description of Related Art
Electrical and electronic devices commonly require either convection or forced-air cooling to maintain safe and reliable operating temperatures. To cool these devices, a heat sink is generally attached to a device package to promote an efficient flow of heat from the device to the heat sink, and from the heat sink to the surrounding environment. As is known, forcing air through or across a heat sink greatly improves its cooling efficiency. To this end, various techniques have been devised for directing air at heat sinks for cooling heat sinked components.
According to one such technique, forced air is directed across an entire circuit board having one or more heat sinked components. Air is made to flow across all components of the circuit board, including both the heat sinked and non-heat sinked components, to provide cooling generally to the entire board. Although this approach is simple and straightforward, it tends to also be inefficient. Particularly when cards are installed in slots of a card cage, heat sinked components tend to block more air than components without heat sinks. This blockage tends to encourage air flow through paths of lesser resistance, around the heat sinks, rather than across or though the heat sinks. Consequently, the components needing the greatest airflow tend to receive the least.
A significant improvement over this approach is to specifically direct airflow to the components that require it most. Air direction can be achieved through air conduits or baffles, which apply intake air directly onto the heat sinks of the most dissipative components. An example of this approach is disclosed in U.S. Pat. No. 5,063,476 to Hamadah et al. There, intake air is directed from an inlet plenum though a series of nozzles and directly onto the heat sinks of components to be cooled. Air flows though and across the heat sinks and exhausts via an exhaust plenum.
Hamadah""s arrangement is particularly efficient; however, it requires significant vertical space above the heat sinks for the inlet plenum, outlet plenum, and nozzles. Vertical space above circuit boards is often in short supply. Circuit boards are commonly installed in card cages that provide slot-to-slot spacing as small as 1 cm. Hamadah""s approach may thus cause circuit boards to require greater distance between slots than they would otherwise require. This means that fewer cards and therefore less functionality can be provided within a card cage.
It would therefore be desirable for a cooling approach to be efficient yet applicable in situations where there is little vertical space above a circuit board.
With the foregoing background in mind, it is an object of the invention to enhance the cooling of heat dissipative electronic components.
To achieve the foregoing object, as well as other objectives and advantages, an electronic assembly includes a substrate, such as a circuit board, and a cover that fits over at least one heat dissapative component mounted on the substrate. The cover is substantially closed against the substrate on all sides except one, where an opening is formed for an air inlet. At least one exhaust opening is formed in the cover above the at least one heat dissapative component. Air flows into the inlet, into the space between the substrate and the cover, and of out the at least one exhaust opening, thus concentrating airflow in the vicinity of the at least one heat dissipative component.